The Study Of Solvent Extraction Process In Caprolactam Purification

Caprolactam is one of the important chemical materials. It is essential to purify the crude caprolactam in order to obtain high-grade caprolactam. Among those purification processes, extraction purification is a frequently-used one and its primary flow path is solvent extraction+water stripping. In the solvent extraction process, water concentration in caprolactam-benzene solution is incremental with increasing of caprolactam concentration in caprolactam-benzene solution owing to the intersolubility of water-benzene-caprolactam. And then hydrosoluble impurities can get into organo-phase through water. So it is important to reduce the water concentration in caprolactam-benzene solution and improve the purification technology of caprolactam.In this dissertation, several correlative influential factors are investigated during the extraction purification process of caprolactam. The experiment results reveal that temperature, phase ratio, pH of feed, caprolactam concentration of feed can affect water concentration and hydrosoluble impurities concentration in caprolactam-benzene solution, while the hydrosoluble impurities concentration of feed has a weak influence . Many actions which including using mixed extractants and pre -treatment of caprolactam-benzene solution after extraction are taken in the dissertation to reduce the water concentration in caprolactam-benzene solution in order to obtain high-grade caprolactam. The experiment results indicate that these methods could partially or greatly, to some extent, lower the conductivity of stripping phase. But they exist some disadvantages each, for example, higher expenditure of energy, lower recovery of caprolactam and so on. Among these methods, the way of adding alkane to caprolactam-benzene solution has a better effect, it can greatly improve the quality of caprolactam although it cause caprolactam partly losing.A modification technology which adds the process of adding alkane to caprolactam-benzene solutionon on current extraction purification process is put forward. Compared to several other techniques on caprolactam purification in recoverity and energy consumption, it is demonstrated that the cost of modified technology is lower than existing technology when purify one ton crude caprolactam. The modified technique is suitable to purify caprolactam and shows great superiority.